This invention relates to an organic electroluminescent (hereinafter referred to as xe2x80x9cELxe2x80x9d) device and a method for manufacturing the same, and more particularly to an organic EL device constructed of a thin film of an organic compound material emitting light due to injection of positive holes and electrons and recombination therebetween while utilizing electroluminescence of the organic compound material, and a method for manufacturing the same.
An organic EL device is constructed into a laminate structure in which a thin film containing a fluorescent organic compound is interposed between anodes and cathodes. In the organic EL device thus constructed, positive holes and electrons are injected into the thin film, to thereby be recombined together, leading to production of excitons, resulting in display being carried out utilizing light (fluorescence, phosphorescence or the like) emitted from the excitons during deactivation thereof.
Now, a conventional organic EL device will be described with reference to FIG. 6.
An organic EL device designated at reference numeral 101 includes a glass substrate 102 made of an insulating and transparent material, on which anodes 103 in the form of a transparent conductive film made of indium tin oxide (ITO) are arranged in a predetermined pattern such as, for example, a stripe-like pattern. The organic EL device also includes an organic EL layer 105 formed of a thin film made of an organic compound and arranged on the anodes 103. The organic EL layer 105 includes a luminous layer. The organic EL layer 105 is formed thereon with cathodes 106, which are made of a thin film of metal such as Alxe2x80x94Li or the like and arranged on the organic EL layer 105 in a predetermined pattern. The cathodes 106 may be arranged in, for example, a stripe-like pattern which cooperates with the stripe-like pattern of the anodes 103 to define a matrix.
In the organic EL device thus constructed, the cathodes 106 are typically formed by PVD such as molecular beam deposition, resistance heating or the like. In the conventional organic EL device shown in FIG. 6, the organic EL layer 105 is covered on a portion thereof on which the cathodes 106 are not to be arranged with masks 112 during formation of the cathodes 106, so that deposition of the cathodes 106 is carried out from above the masks 112. This permits the cathodes 106 to be formed on a portion of the organic EL layer 105 which are not covered with the masks 112, leading to patterning of the cathodes 106.
Unfortunately, formation of the cathodes 106 using the masks 112 requires to increase both dimensional accuracy of the masks 112 and accuracy of positioning of the masks 112 necessary to positionally correspond the cathodes 106 to the anodes 103. In particular, information of a fine pattern wherein the cathodes 106 are arranged in a complicated manner rather than the above-described stripe-like manner defining the matrix, it is required to further increase dimensional accuracy of the masks 112.
Also, formation of the cathodes 106 by means of the masks 112 tends to cause a material for the cathodes 106 to enter or intrude into a portion of the organic EL layer 105 on which formation of the cathodes is not desired such as the portion of the organic EL layer 105 covered with the masks 112 and the like during formation of the cathodes 106. This often leads to short-circuiting between the cathodes 106 which must be electrically separated from each other.
In order to solve the problem, it is proposed to arrange a rib 109 between each adjacent two of the cathodes 106 to separate the cathodes from each other for insulation therebetween, as shown in each of FIGS. 7(a) to 7(c).
In FIG. 7(a), the anodes 103 are previously formed thereon with the ribs 109 and then the organic EL layer 105 is formed on the anodes 103, followed by formation of the cathodes 106. The cathodes 106 are deposited on the organic EL layer 105 while being separated from each other through the ribs 109. Such formation of the cathodes 106 by means of the ribs 109 increases both dimensional accuracy and positioning accuracy of the cathodes as compared with those by means of the masks 112.
However, in formation of the cathodes 106 using the ribs 109 shown in FIG. 7(a), the cathodes which must be separated from each other on both sides of each of the ribs 109 fail to be separated from each other due to adhesion of the cathode material to the rib 109. In order to solve the problem, ribs 109 shown in FIGS. 7(b) and 7(c) are proposed for formation of the cathodes 106.
The rib 109 shown in FIG. 7(b) is formed into a downwardly or invertedly tapered shape in section to prevent the cathode material from reaching a lower portion of the rib 109. Alternatively, the rib 109 may be formed into a T-like shape in section rather than the invertedly tapered shape, resulting in a shade being formed under the rib 109.
The rib 109 shown in FIG. 7(c) is formed into an increased height, so that the cathode material may be obliquely deposited on the organic EL layer 105 from one side of the rib 109. This permits the cathode,106 to be satisfactorily blocked on the other side of the rib 109.
In the rib 109 shown in FIG. 7(b) proposed in order to improve the rib of FIG. 7(a), although the invertedly tapered configuration of the rib 109 effectively prevents the cathode material from reaching the shade under the rib 109, it fails to permit the organic EL layer 105 formed prior. to formation of the cathodes 109 to be formed on the shade of the rib 109. Thus, when the cathode material intrudes into a portion of the anodes on which the organic EL layer 105 fails to be formed, short-circuiting occurs between the anodes 103 and the cathodes 106. Thus, the rib 109 shown in FIG. 7(b) requires to rotate the substrate 102 during formation of the organic EL layer 105, to thereby permit an organic material for the organic EL layer 105 to be deposited under the rib 109. Also, in the rib 109 of FIG. 7(b), it is required to subject the rib 109 to etching to form it into the invertedly tapered shape after such arrangement of the rib 109 on the anode 103 as shown in FIG. 7(a).
In the rib 109 shown in FIG. 7(c), an increase in height of the ribs 109 and oblique deposition of the cathodes 106 on the organic EL layer 105 cooperate with each other to separate the cathodes 106 from each other. However, requirements on an aspect ratio (height/width) in section of the rib 109 renders an increase in height of the rib substantially difficult. Also, the oblique deposition causes a direction in which patterning of the ribs 109 is carried out to be limited to only a vertical direction or a manner in which the patterning is carried out to be limited to only a stripe-like manner, to thereby fail to provide complicated patterning of the ribs 109 which permits bending or meandering of the cathodes 106.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide an organic EL device which is capable of permitting insulation between electrodes during patterning of the electrodes to be reliably and readily ensured.
It is another object of the present invention to provide a method for manufacturing an organic EL device which is capable of reliably and readily accomplishing insulation between electrodes during patterning of the electrodes.
In accordance with one aspect of the present invention, an organic EL device is provided. The organic EL device includes a substrate, on which first electrodes and second electrodes are arranged. The first electrodes and/or second electrodes are formed to be transparent. The organic EL device also includes an organic EL layer including a luminous layer and arranged on the first electrodes. The second electrodes are arranged on the organic EL layer. The organic EL device further includes electrode separation sections arranged so as to separate the second electrodes from each other while insulating them from each other and each including a plurality of insulating ribs juxtaposed to each other at predetermined intervals. The electrode separation sections are arranged on the first electrodes or in proximity to a periphery of the first electrodes.
In a preferred embodiment of the present invention, the ribs each have an aspect ratio in section thereof set to be 1 to 5.
In a preferred embodiment of the present invention, the ribs are so formed that upper ends of side walls thereof opposite to each other respectively project in directions opposite to each other.
In a preferred embodiment of the present invention, the first electrodes and second electrodes are arranged in a stripe-like and so as to define a matrix in cooperation with each other. The ribs each are arranged between the second electrodes.
In a preferred embodiment of the present invention, the first electrodes and second electrodes each are arranged in a predetermined pattern. The ribs are arranged around the second electrodes to which a voltage are concurrently applicable.
In a preferred embodiment of the present invention, an insulating layer is formed on the substrate and around the first electrodes so as to expose a desired luminous section.
In accordance with another aspect of the present invention, a method for producing an organic EL device which includes first and second electrodes, an insulating substrate, and an organic EL layer including a luminous layer and arranged on the first electrodes, wherein the first electrodes and/or second electrodes are formed to be transparent, the first electrodes are arranged on the insulating substrate, and the second electrodes are formed on the organic EL layer is provided. The method includes the steps of arranging a plurality of ribs on each of electrode separation sections for separating the second electrodes from each other in a manner to be spaced from each other at predetermined intervals and positioned on the first electrodes and in proximity to a periphery of the first electrodes, laminating the organic EL layer on the first electrodes from above the ribs, and depositing the second electrodes on the organic EL layer from above the ribs.